Conventionally, scroll fluid machineries are widely used in compressors provided for compressing refrigerant in refrigeration circuits such as air conditioners. In a scroll fluid machinery, a fixed side volute rap and a movable side volute rap are provided at a fixed scroll and a movable scroll, respectively, so as to engage with each other to form a fluid chamber. In the scroll fluid machinery, the movable scroll revolves to change the volume of the fluid chamber. For example, in a scroll compressor, the volume of the fluid chamber in a closed state decreases, thereby compressing the fluid in the fluid chamber.
In this way, the movable scroll revolves with its rap engaging with the rap of the fixed scroll in the scroll fluid machinery. In order to move the movable scroll smoothly, the fixed scroll must be arranged accurately at the position where the rap of the revolving movable scroll evades hard contact with the rap of the fixed scroll. For this reason, the fixed scroll must be positioned accurately in assembling the scroll fluid machinery. Methods and apparatuses for positioning the fixed scroll have been disclosed in Patent Document 1 and Patent Document 2, for example.
Specifically, in the positioning method disclosed in Patent Document, an assembly body is prepared first by assembling a movable scroll, a crank shaft engaged therewith, and a bearing for the crank shaft. Next, a fixed scroll is engaged with the movable scroll of the assembly body, and then, the crank shaft in this state is rotated by a motor. Then, variation in torque necessary for rotating the crank shaft is detected, and a contact degree and a contact direction of the fixed scroll to the movable scroll are calculated on the basis of the detected torque variation. Subsequently, a distance by and direction in which the fixed scroll is to be moved are lead out according to the contact degree and the contact direction of the fixed scroll to the movable scroll, and then, the fixed scroll is moved on the basis of the lead out distance and direction.
Referring to the positioning method disclosed in Patent Document 2, an assembly body is prepared first by assembling a movable scroll, a crank shaft engaged therewith, and a bearing for the crank shaft. Next, a fixed scroll is engaged with the movable scroll of the assembly body, and then, the crank shaft is rotated 90° by 90° in this state by a motor. Wherein, the fixed scroll is moved until the rap of the movable scroll and the rap of the fixed scroll are in contact with each other at each rotation angle 0°, 90°, 180°, 270° of the crank shaft. Then, the position where the fixed scroll is to be arranged is calculated on the basis of the amount of the movement of the fixed scroll in each rotation angle of the crank shaft, and then, the fixed scroll is moved to the calculated position.    Patent Document 1: Japanese Patent Publication No. 05-024356A    Patent Document 2: Japanese Patent Application Laid Open Publication No. 2002-081385A,